Drive for radio tuning mechanism



June 26, 1928.

C. A. PINKHAM' DRIVE FOR RADIO TUNING MECHANISM Filed Jan. 1927 radio dial. Theobjection to such drivesjis Patented June 26, 1928 r A 1,674,738 UNITED ZSFIATFES H CE."

CLARENCE A. JPINK'HAM; or JACKSON nnrenrs, NEW YORK, Assieivonmo ARTHUR V P XnoRsnY, 0F new YORK. 1 1.51, s

nnivnroR 1mm TUNING I mncnnlvisivr.

" Application filed-January s, 1927. "iserieil n o. 159,755.

This inventionrelates broadly to improved driving mechanism for eifecting a nice adjustment of the tuning means em p'loy'ed' in radio apparatus. More particularly, it relates to Vernier drives for radio dials which in accordance with "connnon practice are 'seeured on the condenser shaft. l -lere tofore such drives have' general'ly comprised a driving pinion, the teeth of which are enmeshed with 'coacting' teeth on the found in the presence offlos t motion and back lash in the meshing teeth, such lost motion and bacl: lash preventing the nicest degree of adjustment asis desirable. This objection has become especially serious in present(ilayprodution jobs in whieh-t'lfie interengaging parts'are made up as stamp inns. For the production of such partsin quantity and at a reasonable price tolerances cannot be close. Oaths 0t hand, it is recognized that positive. inter-engagement between the driving shaft and the driven dial is essential in order to maintain at all times a predetermined-, fixed angular relationship between these elen'ie'ntsfIn accordance with the I-present invention it is proposed. to fr etain this'fnecessary re lationship by providing-for' positive interconn eetion between the fdriving" and driven elements whereby their predeter mined liked angular relationship will. preserved but it is further proposed [to improve the driving mechanism therebetween whereby back :lashand lost moton are eliminated. Inv the simplest embodiment of the invention a friction element carried by the driving shaft engages the driven dial operativel y so that-the slightest motion of the driving member imparts acorrespon ding' motion to the driven member without liability of lost motien or backlash therebetwcen. This result is'secured by employ ing a friction drive. The danger of slip;- page in afriction drive or the over-run,- ning of one' member with respect to another is removed by the positive inter-engagement of the driving and driven parts hereinbefore referred to. Such a positive inter-engagement may be secured throughenmeshing teeth.

Reference is now to be had to the accompanying drawings for anunderstanding of a simple and practical embodiment of the in vention wherein: Y Y

latio'n between-the driving and driven ele- [driving and driven elements.

Figure 1 is a viewqin'elevation 0f the cover plate of a radio dial and indicating the provision of a Vernier drive. I

Figure-2 is a view in section on the dial shown in Figure 1 and takenon the plane indicatedfby the line 2 2 andlooking in the direction of the arrows andof the inrproved 'fricti'on' drive with positive interconnection between the driving and driven elements. r

Figure 3 is a fragmentary'view ona larger scale and infro-nt'elevation sho ingthe rements; the cover plate being removed.

Figure 4 is a "fragmentary sectional view on a larger scale taken tlirough'the parts shown in Figure 3 on the line ll thereof and looking in the direction'of the arrows- Astheidescrip'tion proceeds it will be understood that the improvements might be incorporated in other types of drives and apparatus than that illustrated herein but for a: convenient understanding of the most practicalp'resent day use it has been elected to show atun erally a cover plate a revoluble dial 1) journaled onthe cover plate throug'h'a sleeve 0 and adapted to be secured to the condenser shaft, and a vernier drive shaft cl for the dial ournaledin the cover plate and having an operating knob d" on'the front thereof. In using a Vernier drive it is desirable to have the finest possible nicety of adjustment of the dial 1), the graduationsthereon being observable through the windows a} in the n mechanism comprising gen- ,7

cover plate. l/Vhere, as is usua'l,'- a racl:

such as b is stamped alongone edge of an arcuate opening 0 in the dial. reliance is placed upon adriving pinion 0n the vernier. drive shaft for rotation of the dial.

'Any such drive involves inherently back lash or lost motion so in tuning there may be appreciable angular variance between the n It is the principal object of the present invention to provide an improved drive whereby such lost motion and back lash are eliminated. To this end, the driving vernier shaft (5 carries thereon a friction drive disk e which bears againstone face of the tuning dial 6. A practicalform of driving disk 0 is illustrated wherein there is stamped a circumferential rib 6" adapted to have a. line contact with the dial Z). Further, it will be desirable to provide for a slight spring pressure inherent in the friction disk 6 so that the rib 6 will be urged yieldingly into engagement with the dial. The drive thus obtained between the shaft d and the dial 6 is direct and eliminates all lost motion and back lash. A possible objection to such an improved drive is that there might be slippage and necessarily would tend to be slippage when the dial is revolved to one extreme position or the other so that one end or the other of the arcuate slot 5 bears against the drive shaft (Z, in. which case further rotation of the dial positively prevented and continued rotation of the shaft (Z would change the angular relation between it and the dial. It is neces sary to preserve the predetermined angular relationship between the driving and driven elements. Accordingly, there is incorporated in the improved mechanism a positive inter-engagement between the drive shaft d and the dial I) which will prevent relative angular displacement of the disk 6 on the dial 6. The simplest form of such positive interconnection is some type of gearing, either spur, bevel or worm. As shown in Figure 3 the arcuate slot 6 in the dial 5 has along one edge thereof a rack Z). The driving shaft (Z carries a spur pinion (Z2 the teeth of which mesh with the rack Z). Wren the shaftal is rotated for the purpose of driving the dial 6 through the engagement of the disk 6 with its face, the pinion will roll idly on the rack b and positive inter-engagement betw enthe shaft and dial thereby preserved and relative angular dis placement therebetween positively prevented. Assume, for instance, that the dial has been revolved to an extreme angular position in which the end of the arcuate slot 6 is brought into engagement with the shaft d. A further relative movement between the parts is thereafter prevented and relative angular, displacement between the drive shaft (Z and the dial Z) is prevented by the engagement of the pinion teeth d with the rack b.

No mention has been made in connection with the description of .the embodiment of the drive shown in Figure 2 of the driving radius of the disk 6. It will be understood, however, that if this driving radius is not coincident with the pitch line of the pinion d there will necessarily be differential motion as between the driving disk and the pinion (Z and periodic slippage to accommodate such differentialv motion. Such a relationship is shown in Figure 2. This is not a desirable condition. In Figure 4 there is shown a relation of parts in which such a condition is corrected. As there shown friction driving-disks E are mounted at opposite sides of the dial 6 and are of such form and dimensions as to bear against the faces of the dial at a line coincident with the pitch line of the pinion d. This relationship is indicated by the dotted line in Figures 3 and' l. The ribs E on the driving disks E in fact bear against the teeth of the rack b. By means of such coincidence it will be evident that the pinion (i rolls on the rack F) with the same linear speed that the driving disks E revolve. Accordingly, there is no differential movement between the two and no unbalanced pressures tending to cause slippage.

Changes in details of the various elements and other adaptations of the'principle em ployed may be made without departing from the spirit of the present invention.

What I claim is:

1. In radio adjusting mechanism in combination with driving and driven elements, gearing interconnecting the elements to maintain them in predetermined angular relation, the gearing on one of said elements being wider than the gearing of the other element and friction means carried on the thinner element and engaging the teeth of the other element .on the pitch line.

2. In radio adjusting mechanism in combination with driving and driven elements, gearing interconnecting the elements to maintain them in a predetermined angular relation, the gearing on the drivenmeans being wider than that on the driving means, friction discs mounted with the driving means and spaced on either side of the gear carried thereby, and circumferential ribs on the discs engaging the teeth of the driven means in a line contact at the pitch line.

This specification signed this 3lday of December A. D. 1926. i

CLAREN E A. PIN'KHAM. 

